AC Milan boss Stefano Pioli said two of his players - Mike Maignan and Fikayo Tomori - were subjected to racial abuse during his team's win at Cagliari.
Milan's 1-0 victory was vital in the context of the Serie A title race, but it was overshadowed by the ugly events at the end of the game.
Keeper Maignan and English defender Tomori were closest to the home supporters when celebrating their win and when the abuse began, Maignan appeared to encourage it to continue by cupping his ear.
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Unaware of the context, the Cagliari players saw that and it provoked a brawl between the two sides, which Milan legend and now technical director Paolo Maldini stepped in to break up.
"Mike [Maignan] told me it was possible to hear some insults from behind the goal," Pioli told DAZN afterwards.
"It's the first time he reacted like that, so something happened. Tomori also told me the same thing.
"It's always said when these things happen, nobody deserves that."
Cagliari forward Joao Pedro defended his supporters, having claimed he hadn't borne witness to the alleged incident.
"I didn't hear anything," he said. "It's a very delicate matter, but I was basically in midfield at the time.
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"This is not a pleasant situation to talk about, but I have been here for eight years and I will defend the fans because I did not hear anything."
Pedro did however reportedly have a heated exchange with Milan forward Zlatan Ibrahimovic in the tunnel, as per Sky Sport Italia.
Cagliari have been involved in racist incidents on a number of previous occasions, with opposition players Moise Kean and Romelu Lukaku among those to have been targeted in recent seasons.
Milan's win kept them on course for their first Serie A title since 2011. They hold a three-point advantage over Napoli ahead of the final eight games of the campaign.
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